We propose to continue our efforts to characterize the small nuclear RNA's (snRNA's) and acidic nuclear proteins (NP's) found in Amoeba proteus nuclei. By arranging for one or the other class of molecules to be the only radioactive ones in the cells as a result of sequential nuclear transplantations through unlabeled cells and by altering the cellular contents of snRNA's and/or NP's by a number of other micromanipulative techniques, we expect to study: (1) interactions between snRNA's and NP's and interactions between these molecules and DNA and/or chromatin; (2) the role of snRNA's and NP's in transcription and, perhaps, DNA replications; (3) how, if at all, snRNA's and NP's are involved in the "programming" of gene expression; (5) the regulation of DNA replication. In addition, we propose to characterize the apparently unusual ribosomal RNA (rRNA) precursors of A. proteus and its seemingly unusual rRNA gene templates.